There are two main ways to get from Northern Europe to Skopelos:
In the charter season there are flights directly from England, Norway, Sweeden, Denmark and many other countries to Skiathos. From here it is an 18-minute ferry ride.
Outside the charter season (or if the charter tickets are not available) fly to Athens or Thessaloniki, and then either take a local flight to Skiathos or take a bus to one of the many ports with ferries going to the northern sporades where Skopelos is located. (Mantoudi, Volos or Agios Konstantinos) The bus / ferry trip from Athens to Skopelos can take as little as 6 hours and be a quite beautiful trip.
We will of course be glad to offer advise when it comes to planning your trip based on our own experiences with travelling in Greece.